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Clinician's Brief (Capsule)

July 2014

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Feeding Management of the Neutered Cat

In the domestic cat, neutering is a risk factor for obesity, which can lead to diabetes mellitus, constipation, orthopedic disease, altered hemostasis, urinary tract disease, hepatic lipidosis, and skin disease. Clients therefore should be educated about the risk for obesity after their pet has been neutered. Neutering usually occurs during a growth period.

Kittens require a specific balance of nutrients to support normal development, so food designed for growth should be fed until ~1 year of age. The age of neutering does not appear to affect the risk for obesity; therefore, weight management strategies could wait until the kitten has finished growing. Factors to consider when educating clients include avoiding free feeding and maintaining strict adherence to daily caloric consumption. Determining a cat’s energy needs after neutering should be based on food intake before neutering, if known. However, the dietary restriction necessary to avoid weight gain can vary for each individual, underlining the importance of ongoing monitoring and adjustment of food intake.—Larsen JA

Canine Renal Disease: When Is the Right Time to Strike?

Evidence-based feeding strategies for canine renal disease are lacking for International Renal Interest Society (IRIS) stages 1–2. Dogs with renal disease (any stage, particularly stage 1 or 2) should be assessed regularly to ensure overall health and nutrition status by scoring muscle condition, body condition, and body weight. Stage 3 (defined as creatinine >2 mg/dL) may be the point at which dietary intervention involves restriction of protein, phosphorus, and sodium. For dogs at stage 2 or less, the general guideline is the same as the minimum adult daily requirement: 1 g protein/lb body weight (senior dogs may need up to 50% more). Avoiding excess phosphorus intake is suggested at IRIS stage 2, rather than implementing a therapeutic renal diet, unless serum phosphorus levels are elevated (>4.6 mg/dL). Finally, supplements (eg, omega-3 fatty acids) may help suppress inflammation and platelet aggregation, lower blood pressure, and modify renal hemodynamics. Because data do not support omega-3 fatty acid intake amounts in patients with renal disease, total daily intake should be calculated to avoid oversupplementation.—Churchill J

How I Feed: The Underweight Senior Cat with Multiple Problems

A significant portion of senior cats, whose nutritional requirements differ from younger cats, are underweight; senior cats with underlying medical problems should consume regular feedings to achieve or maintain ideal body condition. In this case, a 9-year-old spayed cat previously diagnosed with granular lymphoma affecting the liver and mesenteric lymph nodes failed to gain weight despite placement of an esophagostomy tube. The cat was tube fed 60 mL q6h of a canned recovery diet that provided 288 kcal/day. The cat transitioned to a canned recovery diet and canned liquid diet blend given q12h to provide 320 kcal/day. The owners were advised to encourage oral food consumption before tube feedings. Within 2 months, the cat’s weight went from 4.45–5.3 kg. This case illustrates the need to prioritize a patient’s current problems and develop a feeding plan based on disease severity and the patient’s appetite level, while minimizing refeeding syndrome in hyporectic patients. Cachexia (loss of lean body mass in patients with neoplasia or other chronic diseases) is common in senior cats with underlying illness and requires appropriate caloric intake to decrease its effect on morbidity and mortality. Fish oil omega-3 fatty acids have been found useful in some patients with cachexia and can be administered through a feeding tube.—Lenox CE

Management of Overweight Dogs & Cats with Cancer

Malnutrition typically associated with cancer patients is known as cancer cachexia, a protein-energy malnutrition characterized by weight loss (WL), fatigue, anemia, and loss of lean body mass and adipose tissue. However, strong association between obesity and malignancy is becoming more apparent. In humans, an increased association between obesity and certain cancers, as well as difficulties in neoplastic disease treatment after diagnosis, has been found. People with established obesity have shorter survival times and higher death rates after cancer has been diagnosed than do people with a healthy body weight. This same relationship has not been fully documented in dogs and cats but may be similar based on early endocrine studies. Thus, development of a WL program for obese dogs and cats with established neoplastic processes may be beneficial. First, it is necessary to determine whether WL offers effective clinical benefit; if not, the time and energy involved in successful WL are not worthwhile. Next, appropriate energy intake for safe WL should be calculated and a diet chosen. For cancer patients, rations typically deliver 35%–50% of calories as protein, contain few carbohydrate calories, and are high in fat. Owners should receive strict feeding guidelines; WL should be monitored to ensure that weight is not being lost too quickly. Once a target weight has been achieved, a maintenance diet can be selected.—Mauldin GE

Adapting to a New Diet During Dog Domestication: Implications for the Domestication Process & Dog Health

The genomes of dogs and wolves were compared to map the selection process during domestication. Thirty-six genomic regions were identified as significantly different between dogs and wolves. Using gene ontology (GO) analysis, genes within these regions were functionally characterized into 2 major themes: nervous system development and digestion.

During dog domestication, selection for 3 starch digestion genes (ie, AMY2B, MGAM, SGLT1) was affected. The pancreatic amylase gene (AMY2B) is responsible for initiating starch digestion in the small intestine. Quantitative PCR analysis showed that repeated gene duplications in dogs resulted in an average sevenfold increase in AMY2B gene copies; this is associated with higher expression of the gene. The MGAM gene, responsible for hydrolysis of maltose to glucose, is located in a region on chromosome 16 that is highly divergent between dogs and wolves. The SGLT1 gene resides in a region on chromosome 26, which also differs markedly between dogs and wolves. SGLT1 is responsible for assisting with glucose absorption through the sodium–glucose cotransporter in the small intestinal wall.

It is believed that such adaptations allowed the ancestors of modern dogs to thrive on a relatively starch-rich diet, an important step in domestication. However, strong variability in AMY2B copy number and widely varying serum amylase activity values among dogs indicate that the ability to handle starch may vary individually and among breeds.—Axelsson E

Evolutionary vs Evidence-Based Diets

Pet owners may consider evolutionary diets (eg, biologically appropriate raw food [BARF]) to mimic the natural diet of their pet’s wild ancestors. These diets may lead to serious malnutrition when devised by nonexperts; however, this does not mean that scientific knowledge cannot be applied to create nutritionally balanced evolutionary diets by applying evidence-based medicine (EBM) principles.

An EBM approach to nutrition should address questions regarding industrial processing effects, nutrient requirements, hygienic risks, possibility of feed contamination, and more. A literature review should provide valid supportive evidence to answer these questions. The effects of food processing extend beyond nutrient availability. Different starch types affect digestibility and microbial activity. Food particle size can impact microbial flora. Because nutrient deficiencies and excesses, insufficient food hygiene, and food contamination can cause life-threatening or crippling diseases, good nutrition can help avoid such problems. If potential risk is associated with a given diet or food, the risk cannot be disregarded until EBM justifies the diet’s safety. Scientific progress necessitates continual literature review, which has resulted in revised dietary recommendations.—Kienzle E

Towards Optimizing Feline Nutrition: Insights from the Dietary Nutrient Profile of Feral Cats

Feeding a natural diet to domestic cats is a popular trend in feline nutrition, but to what extent can this nutrient profile be considered optimal? Prey items ingested by feral cats included mammals (78%), birds (16%), reptiles and amphibians (3.7%), and invertebrates (1.2%). The nutrient profiles of 27 dietary prey items ingested by feral cats were averaged and compared with average nutrient profiles of commercial feline dry diets. Nutrient profile analysis of feral cats showed that 52% of daily energy intake is derived from protein, 46% from fat, and 2% from nitrogen-free extract (NFE). NFE content in feline commercial foods is mainly derived from cereal grain starch, which is generally well digested.

The health effects of long-term carbohydrate intake in domestic cats are not clear. Dietary protein and phosphorus content of prey items ingested by feral cats are higher than the physiologic minimum requirement, which may pose a risk for cats with impaired renal function. Nonnutritive properties (eg, feed consistency, texture) play an important role in maintaining a balanced microbial population in the GI tract; these factors should be considered when optimizing feline diets. Valuable insights may be gained by studying the natural diets of feral cats, although severe physiologic and climatic conditions faced by feral cats differ markedly from the more sedentary lifestyle of domestic cats.—Hagen-Plantinga EA

Raw Meat-Based Diets: Current Evidence Regarding Benefits & Risks

High-quality studies evaluating raw meat-based pet diets (RMBD, commercial or home prepared) are limited. RMBD consumption is associated with certain risk factors (eg, nutritional imbalances, dental fractures, GI trauma, exposure to pathogenic bacteria, viruses, protozoa not killed during cooking). RMBD may contain potentially harmful nutritional imbalances (eg, inadequate vitamin A and E levels, excessive vitamin D, inappropriate calcium:phosphorus ratio). Diets containing bones pose the risk for GI obstruction or perforation; no known studies have evaluated the risk for dogs fed raw bones versus cooked bones. Feeding RMBD is a known risk factor for various pathogens (eg, Salmonella spp, Escherichia coli, Toxoplasma gondii, Neospora caninum). Of dogs fed RMBD, 3%–50% shed Salmonella spp in their feces; cases of human salmonellosis resulting from direct or indirect contact with dogs have been documented. Benefits ascribed to RMBD include improved skin and coat quality, improved digestibility, improved immune function, and decreased incidence of numerous medical conditions. Some claims may be based on anecdotal evidence rather than scientific study, however. In addition, most home-prepared RMBD have been found to be deficient in 1 or more essential nutrients. These diets should be reviewed by board-certified veterinary nutritionists and owners counseled on the potential risks.—Hamper BA

Systemic Illness: The Role of Oxidative Stress & Antioxidant Supplementation

The endogenous antioxidant network is made up of thiol antioxidants (eg, glutathione, cysteine), scavenger enzymes (eg, glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase), lipids, water-soluble vitamins (eg, A, C, E, betacarotene), and trace minerals (eg, selenium, zinc, iron, manganese, copper), which modulate or quench reactive oxygen species (ROS) and maintain cellular homeostasis and redox balance. Because oxidative stress plays a role in the pathogenesis of many acute and chronic diseases (eg, hepatopathies, drug-associated toxicoses, heart failure, chronic kidney disease [CKD], chronic inflammatory disease, diabetes mellitus) antioxidant supplementation may be a logical step in disease treatment. Patients with liver disease tend to have low glutathione concentrations, which can contribute to hepatocyte damage and disease progression. Oral administration of glutathione precursors (ie, SAMe, N-acetyl cysteine, silibinin) to liver disease patients can lead to increased glutathione concentration. Despite a paucity of data, vitamin E supplementation has been used in dogs and cats with liver disease, as some human studies have shown benefits. Dogs and cats with CKD would likely benefit from dietary antioxidant and/or vitamin supplementation. Antioxidant supplementation in ill dogs and cats has been largely extrapolated from data on humans and a limited number of species-specific controlled clinical trials; more research is needed.—Viviano KR

The Long-Term Health Effects of Spay & Castration for Dogs

Research is emerging on the long-term effects of surgical sterilization of pet dogs and cats. Because sterilization involves removal of the entire organ system and its endocrine axis, substantial and widespread effects should be anticipated. Most published data support the finding that sterilized dogs have a longer lifespan as compared with intact dogs, although information regarding when pets were sterilized is lacking. Classifying dogs as sterilized or intact at time of death without knowing when sterilization occurred could misrepresent the beneficial effects of maintaining exposure to sex hormones for any length of time before sterilization. One study of female rottweilers identified a beneficial effect of duration of intact status on lifespan. The effects of sterilization on specific areas of development were explored (eg, behavioral effects, growth and musculoskeletal development, weight gain, activity level, training, cortisol axis). Studies also have examined the effects of neuter status on the risk for developing a particular disease (eg, cancer, urethral sphincter mechanism incompetence, musculoskeletal disease [eg, hip dysplasia, cranial cruciate ligament rupture], others). Growing evidence indicates that sterilized dogs and cats have different risks for certain diseases than do intact animals, but further research is needed.—Creevy KE

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